Tomas Berdych put his poor start to the ATP World Tour Finals behind him by defeating Marin Cilic in another one-sided clash at London's O2 Arena.

The pair both lost their opening matches 6-1 6-1, with Berdych beaten by Stan Wawrinka and Cilic losing to Novak Djokovic in the joint heaviest defeats since the tournament moved to Britain in 2009.

Berdych showed much improved form this afternoon but US Open champion Cilic was still well below his best and succumbed 6-3 6-1.

This was revenge for Berdych, who lost to Cilic both at Wimbledon and during the Croatian's stunning run in New York.

Cilic found the best form of his career to beat Berdych, Roger Federer and Kei Nishikori all in straight sets over the final three rounds and lift the title.

But the Cilic of New York has been nowhere to be seen in London and he could not have made a worse start against Berdych, losing his opening service game.

He had two chances to make it 4-4 but could not take either and a second break for Berdych gave him the first set.

The second was even worse for Cilic and Berdych easily completed the seventh successive straight-sets win of the tournament.

The Czech maintained his odd record of having lost his first match and won his second on each of his five appearances in London, which has only once been good enough to take him through to the semi-finals.

The result means Wawrinka can qualify for the last four tonight with victory over Djokovic, but the world number one will have to wait until his final match whatever the result.

Even with his poor record, Cilic is not yet eliminated, but it would take a hugely unlikely sequence of events for him to go through.